This invention generally relates to carrier acquisition of a digitally modulated signal. Specifically, the present invention relates to the carrier acquisition of a Time Division Multiple Access (TDMA) digitally modulated signal. More specifically, the present invention relates the carrier acquisition of a TDMA digitally modulated signal employing staggered formats.
Conventional TDMA carrier acquisition circuits employ the same data detector for both the preamble field and the data field. This allows the carrier phase to lock in an ambiguous phase state. The carrier phase state is then resolved by the detection of the unique word (UW). The resolution of the carrier phase ambiguity requires multiple UW detectors.
An approach for improved carrier acquisition is shown in U.S. Pat. No. 4816775 entitled "Negative feedback, phase rotation, phase acquisition and tracking apparatus and method". This invention describes data detection circuits and modifications to the previously patented approach that result in improved UW detection performance and reduced hardware complexity. In particular this invention applies to staggered modulation formats for use through non-linear channels.